FIELD OF THE INVENTION
The present invention relates to a packaging machine for continuously packaging products with synthetic resin film, and in particular to a packaging machine for sealing products by evacuating the bags made of synthetic resin film and containing the products, by means of an evacuator.
The conventional shrink-packaging machine comprises a heat tunnel. Products are inserted, each into a sheet of center-folded film made of synthetic resin. Each sheet of film, containing a product, is heat-sealed at the open side and the open ends, into a bag. The bags containing the products are passed through the heat tunnel, one after another, and are heat-shrinked as they pass through the heat tunnel. Before each bag is passed through the heat tunnel, small holes are made in the bag to allow the passage of air in order to achieve successful shrink-packaging, and a member made of foamed rubber is pressed onto each bag, thereby removing the residual air from the bag.
In another conventional; vacuum-packaging machine, products are inserted into prepared bags made of synthetic resin, and the bags containing the products are evacuated by means of a vacuum pump and then sealed at their open ends.
In the case of the first machine, the small holes of each bag remain open even after the products have been shrink-packaged. Dust or bacilli inevitably enter the package through these holes. Due to these holes, the bags cannot contain liquid, nor can they be used to provide airtight packages.
In the case of the second machine, the products must be inserted into the bags, which requires much time. Further, each bag must be sealed at its open end after the product has been inserted into it. Moreover, bags of different sizes must be prepared for packaging products of different sizes. Obviously, this machine cannot accomplish automatic packaging.